Federal regulators have given the go-ahead for the first new offshore drilling project in the Gulf of Mexico since last year's massive oil spill. (MMS photo)

The company would still have to pursue — and get approval for — a separate permit to drill before it could launch work on that well.

The government has previously approved two supplemental exploration plans — both filed by Shell Oil Co. — that made changes to pre-approved, existing drilling plans. By contrast, BHP Billiton’s proposal is entirely new and had not won any government approval prior to last year’s spill. Energy analysts had been watching for the approval of an initial exploration plan as a last, major milestone in restarting Gulf drilling.

In approving BHP Billiton’s initial exploration plan, the ocean energy bureau assessed the environmental consequences of the company’s proposed drilling and concluded there would likely be “no significant impact” from the work. That site-specific environmental assessment is required under a federal statute known as the National Environmental Policy Act. But before the spill, federal regulators routinely waived such environmental assessments for proposed offshore exploration plans.

According to BOEMRE, the site-specific environmental assessment included new information that had not been previously available for analysis. After concluding that the proposed drilling would not significantly affect the quality of the environment, the ocean energy bureau determined that additional environmental reviews were not necessary.

BHP Billiton’s exploration plan covers its proposed well in Green Canyon Block 653. The ocean energy bureau began reviewing it on April 1; after BHP Billiton revised and resubmitted the proposal, the agency started a new examination on April 28.